The invention relates to a mixing apparatus comprising at least one mixing vessel having a side wall and a vertical axis, and comprising in the vessel a mixing screw driven from its upper end by drive mechanism, the mechanism supporting the screw at its upper end for rotation simultaneously around its axis and around the vessel axis. The lower end of the mixing screw shaft is supported in a bearing adjacent to the vessel bottom. The bearing structure includes a universal joint as well as radial and axial force receiving bearings.
Such mixing apparatus is known. A support structure having a universal joint and radial and axial forces receiving bearings are necessary for larger mixing apparatus. This is contrary to smaller mixing apparatus in which the forces are smaller, e.g. as according to the Dutch Pat. No. 110,847 and the Dutch Pat. application 7408885 (laid open for public inspection on Jan. 5, 1976),
In a known construction developed by Applicant the lower end of the mixing screw shaft is connected by the universal joint to a short vertical shaft supported in the radial and axial force receiving bearings which are provided in a bearing housing fixedly secured below the mixing vessel bottom. The universal joint is situated above the bottom wall of the vessel and in the material to be mixed. Since the joint carries out a somewhat pumping movement during the operation of the mixing apparatus, the material to be processed may be damaged, dependent on the nature thereof. At the same time the joint wears and worn particles or lubricant matter may contaminate the product.
One could avoid such disadvantages by positioning the vessel bottom over the universal joint. However, this meets with the difficulty of providing sealing between the vessel bottom and the bearing housing due to the pivotal movement of the screw shaft adjacent to the bottom.
The present invention provides, starting from Applicant's earlier construction, a solution whereby the first-mentioned disadvantages are eliminated. A further solution is obtained for the sealing at the bottom while a conpact design of the supporting structure is obtained.